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  • During thermal cycling the samples are subjected

    2018-10-31

    During thermal cycling, the samples are subjected to thermal changes and also to additional exposure to water. The main cause for the reduction in bond strength after thermocycling is believed to be the possible effect of hydrolysis at the interfaces of the bonding resin and hybrid layer [48]. Water molecules are absorbed during TC into composite resin and fiber posts by diffusion, which is a time dependent process [49,50]. This could be the basis for the lower bond strength values obtained after thermocycling in the present study. However the difference was not statistically significant. After assessment of failure mode using magnifying lens, adhesive failure at cement–dentin interface, cement–composite interface, composite-post interface, cement-post interface, and cohesive failure within cement layer were detected with different ratios, Table (3). Generally, in relined group, most failures occurred at the interface between the cement and root dentin. Bonding to dentin is a more difficult process due to the anatomical and histological characteristics of dentin as well as the smear layer on the cut dentin surface [51]. The peculiar conditions of hydration in dentin on endodontically treated canal walls [51], the degradation of dentin collagen [52], the effect of irrigation and eugenol-containing root-filling material, the regional differences in the density of the dentinal tubules [53], and the fluidity of the bonding materials [38] are all variables that can possibly influence the quality of adhesion at the cement∖dentin interface.
    Conclusions Within the limitations of the present study the following could be chemicals informative post concluded:
    Introduction Preeclampsia is a disorder of worldwide significance and specific to pregnancy, it affects 5–10% of pregnancies. It is the third most common direct cause of maternal death in the United Kingdom and accounts for up to 40,000 pregnancy-related deaths per year in the developing world, also it may lead to obstetric morbidity and accounts for 25% of preterm deliveries which in turn result in adverse neonatal outcome [1,2]. It occurs usually after 20 weeks of chemicals informative post and is characterized by normal vascular response to placentation manifesting as generalized vasospasm, activation of coagulation system, reduced organ perfusion affecting the kidney, liver and brain. It requires both blood pressure exceeding 140/90 mmHg after the 20th week of gestation and proteinuria exceeding 300 mg in a 24 h urine sample [3,4]. Periodontitis is regarded as a chronic inflammatory oral infection that affects the tooth supporting structures and bone, in which bacteria of dental plaque and calculus and their byproducts are the principal etiologic agents. It is well known that teeth, gingival margins and periodontal pockets are places that could harbor bacterial colonization, and that one cubic millimeter of dental plaque contains about 100 million bacteria [5–7]. While pericoronitis is an inflammatory condition that may accompany the partially erupted teeth, the Gram-negative anaerobic bacterial growth that develops in the distally located coronal flap is the major cause of this condition. It is generally agreed that this process is potentiated by food debris accumulating in the vicinity of the operculum and occlusal trauma of the pericoronal tissues by the opposing tooth. Pregnancy and fatigue are associated with an increased occurrence of pericoronitis [8,9]. It is generally accepted that unhygienic oral conditions that results in inflammatory effects as in periodontitis and pericoronitis could negatively affect the general health of individuals. A cause and effect relationship between the health condition of the oral cavity and some systemic diseases is attributed to the presence of dental plaque, periodontal and pericoronal infections [10]. There is growing evidence that suggests an association between chronic oral infection and various systemic diseases, diabetes mellitus, preterm birth and low birth weight. Accordingly, a positive clinical association between preeclampsia and chronic periodontal or pericoronal infections has been hypothesized. Since both periodontal and pericoronal infections are chronic Gram-negative infections proposed to feature a chronic endotoxins burden that may result in transient translocation of the organisms to the placenta, thereby triggering placental inflammation [11–13].